ATP receptors have been shown to be present on a wide number of different cell types (Dubyak et al Am J Physiol (1993) 265, C577-C606). Neutrophils, monocytes and macrophages have been isolated from several species including humans and ATP and/or UTP have been shown to increase intracellular calcium levels. Activation of these receptors on leukocytes can either directly stimulate certain types of inflammatory response or can prime the effector cells to other inflammatory mediators in vivo. ATP can upregulate the expression of adhesion molecules (Freyer et al J Immun. (1988) 141, 580-586) which causes enhanced adhesion of circulating leukocytes to endothelial cells and their enhanced migration into the tissue space. ATP has also been shown to promote chemotaxis of both neutrophils and eosinophils (Verghese et al J. B. C. (1996) 271, 15597-15601 and Burders et al Blood (1993) 81, 49-55) which may promote an inflammatory response. ATP priming of neutrophils can also potentiate superoxide production (Seifert et al Eur J Biochem (1989) 181, 277-285). ATP receptors are also present on a number of other cell types such as chondrocytes, keratinocytes, microglia and goblet cells (Leong et al BBA (1994) 1201, 298-304; Pillai et al J Clin Invest (1992) 90, 42-51; Walz et al J Neuroscience (1993) 13, 4403-4411 and Abdullah et al Biochem J (1996) 316, 943-951). Stimulation of the receptors on these cells can stimulate or enhance inflammatory responses and antagonist of the receptor may therefore be of use in a number of inflammatory diseases such as asthma, inflammatory bowel disease, ARDS, psoriasis, rheumatoid arthritis, myocardial ischaemia, COPD, cystic fibrosis, arthereosclerosis, restenosis, peridontal disease, septic shock, osteoarthritis and stroke. ATP receptors have also been reported on tumour cells (Dubyak et al J. Biol. Chem., (1985) 260, 10653-10661 and Wagner et al Gastroenterolgy, (1997), 112(4) suppl. page A1198) and may be involved in the development of cancer. Antagonists may therefore be useful in treatment of cancer.